Conoscope



June 20, 1944.

W. L. BOND C ONOSCOPE Filed Dec. 19, 1942 s sheets-sheet 1 ATTORNEY D mm B 5. WL W 5, y

w mm brat. wk N Qk June 20, 1944.

A ANALYZER w. L. BOND CONOSCOPE I 3 .Sheets-She'et 2 Filed Dec. 19, 19.42

LIGHT LIGHT SOURCE POLAR/25R LENS ANALYZER IA IVEI VTOR I W. L.'BOND i- V-L ATTORNEY sauna:

1 Z 5: I I muklzsn w. L.- BOND June 20, 1944.

CONOSCOPE Filed Dec. 19, 1942 s Sheets-Sheet s IN I/E N TOR W. L. BOND BY A TTORNEV tank and for manipulating the crystal is assured.

reams June 20, 1944 FICE conoscora Walter L. Bond, Brooklyn, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation oi New York,

- Application December is, 194:, Serial No. 469,520

9 Claims. This invention relates to a conoscope and more particularly to a cono'scopeoi. the immersion An object of the invention is to facilitate'the preparation and testing ofcrystals. t

A more specific object oi the invention isto Fig. 4 is a perspective view oi a fixture that may be used for adjustably supporting a crystal .during examination by the conoscope;

facilitate the examination by means of polarized light of crystals of varying sizes and types.

In accordance with a specific embodiment of the invention a novel conoscope is provided which comprises an immersion tank, a rotatable work supporting platform within the tank and two opti- Fig. 5 is a perspective view of another fixture that may .be used for adjustably supporting a partially completed crystal plate during examination by the conoscope; and

Fig. 6 is an elevational view of a tool that may be, used in adjusting the fixture 0'! Fig. 5.

Referring now to the drawings, the conoscope illustrated includes immersion tank il, two lens cal systems which include. respectively, a light polarizer and an analyzer and which are .arranged horizontally with respect to the tank.

The crystal to be examined is positioned within the tank on the rotatable platform and is prefer-- ably immersed in a fluid which has the same, or approximately the same, index of refraction as the crystal being examined.

In accordance with a feature of the present invention the optical systems are arranged horizontally with respect to the tank whereby free and unobstructed access from above for filling the In accordance with another feature of the invention the tank is free of traversing shafts and the like whereby relatively large crystals may be accommodated.

In accordance with still another feature-of the invention the arrangement of the optical system is such that a "universal focus is attained, that is, variousfluids having different indices of reshaft 28.

tubes l2 and I3 arranged horizontally with respect to tank ii and terminating in respective ports provided at'diametrically opposite points inthe wall thereof, and three supporting legs It, i! and ii for supporting the conoscope assembly.

Tank Ii is provided with cover2i which is hinge supported to permit movement between closed and open positions. Supporting leg it carries horizontal extension arm 22 which supports lamp housing 23.

Platform 24 is rotatably supported inside tank 8 I; platform 24 may be rotated from the exterior oi tank ii by means of hand-wheel 2B, the platform and hand-wheel being coupled through Suitable packing and bushings are provided to prevent leakage of fluid from tank ii around shaft 28. Table 38 is'removablysupported fraction may be utilized without necessitating any change in lens settings. This is a particularly valuable feature as it facilitates the use of the conoscope for examination of diiierent types'of f crystals, for example, quartz and Rochelle salt.

A complete understanding of the novel arrangement contemplated by the present invention as well as appreciation of the various valuable features thereof may be gained from consideration of the following detailed description and the anwhich embodies features of the present invention,

on platform 24 and is rotatable therewith. Trans-i parent end plate 89 is attached to table 88 and provides, in conjunction with spring clip to, convenient means for supporting small and fragile objects being examined such as piezoelectric plates. The angular position of platform 28 within the tank may be determined byobserving the relative sitions of graduated dial ti (rotatable with shaft 28) and fixed viernier 42. Lamp 48 is provided for illumination of the dial and vernier. Valve 48 (Fig. 3) is provided in the base of I. I I for'drainage of liquid therefrom when desired. Coming now to the optical and lens system, let

:us consider first the contents of lens tube is,

reference being made both to Fig. l andto Fig. 2.

Starting at the end of tube i2 nearest to'lightsource II, which may be, for example, a lamp of the mercury vapor type, and moving toward tank ii, we first. encounter light polarizer 53 which may comprise a polarizing film mounted between two plates of glass. I

Polarizer 52 is mounted in carriage El; carriage 83 and polarizer 52 maybe rotated, within limits,

insidetube I: by means of lever. for a purpose that will be describ d subsequently. so 7 The next element of the optical system encounoptical system located in lens tube I! are to polar- -ize the'light produced by source ii, to filter out all portions of the light except the green light and to cause the polarized green light to converge and to enter the crystal under examination in a cone of rays.

It will be noticed that concavo-convex lens I2 and similar concavo-convex lens II (of the optical .system contained in lens tube ll which will be described subsequently) are mounted in the two ports provided at diametrically opposite points in the wall of tank II, the lenses acting as means for closing the respective ports to the passage of fluids; It should also be noted that the design of lenses 1-2 and 13 is such that the respective inner faces of the two lenses may be considered as beaasao'm which may be rotated, for a purposeto be described subsequently, by means of handle sl which is coupled to the carriage by, suitable gearing.

Eyepiece 82 is positioned at. the end of lens tube ll.

The purpose, in general, of that portion of the optical system housed in lens tube i3 is to correct the divergence of the light rays so that the eye may focus them for the retina and to analyze the light rays.

As clearly shown in Fig, 2 both sets of lenses, i. e.,' the set positioned in lens tube i 2 and'the set positioned in lens tube i3, act to cause convergence of a diverging group of light rays.

The conoscope of the present invention may be used to advantage in making various types of observational tests on different crystalline materials. For example, it may be desirable to locate the so-called "Z or optic axis of quartz piezoelecing segments or lunes of a single imaginary sphere.

This is clearly shown in Fig. 2, the surface of the imaginary sphere being indicated by the "dotand-dash circle. with this novel design of lenses, light rays projected from the center of the imaginary sphere will always strike the inner surface of the respective lens at right angles thereto regardless of the direction of the rays.

As will be more apparent from subsequent porfraction of the beam of light by uneven surfacesw of the crystal being examined; the index of refraction of the fluid should-match that of the crystal in order that the light rays will not be bent in passing between fluid and crystal. Thus a difierent fluid,-i. e., difierent-with respect to refractive index, would preferably be utilized during examination of quartz crystals than that utilized during examination of Rochelle salt crystals; the novel arrangement of lenses referred'to above permits ready change from one fluid to another as different crystalline materials are examined without necessitating any change in the optical system.

Considering now the portion of the optical system housed in lens tube, It, concavo-convex lens 1.3 has been referred to above. We next encounter, in order, a pair of piano-convex lenses 1! and 15, arranged back to back, and concavo-convex lens 16. The next element encountered is reticule 11, i. e.. the fcrosshairs" element. The reticule may, for example, be a glass disc having fine lines scratched. thereon at the desired points, these lines being filled with black pigment.

The next element of the optical system is analyzer 80 which may comprise a polarizing fl-lm mounted between glass plates. As shown in Fig. 1, analyzer 80 is mounted in a rotatable carriage tric crystal iill. To carry out a test for such purpose crystal llil would be positioned on table 38. as shown in Fig. 1, and tank Ii filled with a suitable liquid, that is, one having an index of refraction the same as, or closely approximating,

that of quartz. (Cover 2| may, as'pointed out above, be opened to permit filling the tank and manipulating the crystal.) Among immersion liquids which applicant has found satisfactory for use during examination of quartz is a mixture of dimethyl phthalate and dichlor naphthalene in the approximateproportions (by weight) of 73.9 and 26.1, respectively.

It should be noted that in accordance with the novel arrangement of the present invention, tank 'H is entirely free of traversing shafts whereby relatively large crystals may be accommodated and whereby free access to the tank is provided for filling the tank and for manipulating the crystal.

Light from source 5|, after polarization by polarizer 52 and after being filtered by light filter I! so that only the green rays remain, is caused to converge by the lenses positioned in lens tube i2 and enterscrystal [0| in a converging cone of light rays. quartz crystal I01, pass through the correction lens system positioned in lens tube l3, through the reticule 11 which, as pointed out above, has "cross-hairs" marked thereon, and is then analyzed by analyzer l0.

Now it is known that if a ray of divergent or convergent plane polarized light i be passed through a crystal parallel to the optic axis thereof and viewed by an analyzer, a system of concentric rings may be seen and that these rings occur only when the direction of the rays of light coincides with the optic axis of the crystal. The observer in the presentinstance, therefore, observes the light :ays through eyepiece 82 and rotates hand-wheel 25 (and platform 24 and table 38 upon which crystal IOI is mounted) until the identifying system" of concentric rings is seen.

Upon occurrence of these rings he knows that.

crystal Illl is now in a position wherein its optic axis coincides with the direction of the rays of polarized light. Indication of the degree of totation of platform 2l.is given by scale II.

The crystal may be tested in various other ways by the conoscope of the present invention; for example, it way be tested for the presence or absence of twinning. To facilitate certain of these tests and to make the conoscope more adaptable to examination of various diiferent materials, polarizer 52 may be rotated 'within. limits in lens tube II by lever 54 and analyzer The light rays, after passing through ll may be rotated in lens tube 13 by lever ll.

The handedness of quartz crystal ill may be -determined by observing whether rotation of analyzer 80 results in expansion or contraction of the system of conoentricrings referred to above.

The conoscope may be utilized also for testing finished quartz plates. In such case the'ilnlshed plate, usually a relatively thin and fragile object,

be replaced by'another having a different refractive index inorder to match the index of a different type of crystal being examined. In fact the focus remainsthe same even if the tank contains only air. 'I'hisfact adds to the practical usefulness of the con'oscope, particularly in shops where crystals of various materials are being may be held in place against transparent end plate 39 by spring clip lll. Platform 24 is now rotated by hand-wheel 25 to the point .at which the concentric ring system will be seen if the quartz plate has been out at the proper angle.

If the ring system is not visible,-the amount of,

rotation of platform 24, as read on scale 4|, required to bring in the concentric ring system will provide an indication of the magnitude of error present in the quartz plate being checked. The conoscope of the present invention is particularly well adapted to the examination of very thin plates in view of the provision of strongly convergent lenses.

The conoscope may, of course, be used for testing crystals other than quartz. For example, let us assume that a Rochelle salt crystal is to be tested. It would be placed on table 38, as was quartz plate IM, but the liquid provided in tank H for examination of the quartz crystal would now be replaced by a liquid having an index of refraction the same as, or closely approximating,

system invented by applicant issuch that no adjustment thereof is necessary. In particular, this is due to the novel design of concave-convex lenses I! and 13 whereby the; respective inner surfaces are so. related that they may be con-- sidered surfaces, or lunes. of-the same imaginary sphere. By virtue of this novel arrangement, whereby. the rays will always strike the inner surface of a respective one of the concavo-convex lenses at right anglesfthereto so long as they are projected to, or are coming from, the center point of the sphere and are not refracted during passage through the tank, the light rays, which are processed and tested.

Referring now to Fig. 4, there is illustrated a fixture which may be used to advantage in supporting a piezoelectric crystal during examination in the conoscope described above and during subsequent sawing of the crystal plates. As shown, the fixture comprises a base plate I i l and a platform H2 tiltably and rotatably supported v by base plate III, the quartz crystal H! which is to be examined and sawed being temporarily attached, for example by useof an adhesive, to

the under-side of platform H2. Crystal ill in this-instance is assumed to be mounted with its Z or optic axis roughly parallel to the longer axis of'base plate ill.

Platform m is tiltably supported with respect to base plate ill by two pinion screws, pinion screw 'I it, and asimilar pinlon'screw not shown but located diametrically opposite to pinion screw I, The amount and direction of the rotation or tilting of'platform I about the two pinion screws, i. ,e'., about axis Ar-iii; is controlled by adjusting bolts III and III which are positioned in base plate ill with, their tips projecting into engagement with the upper surface of platform H2. For example, clockwise rotationof platform H2 will be caused by retraction of adjusting bolt III and a corresponding projection of bolt lit.

. Platform m',to.sethor with supporting yoke ill is rotatable about 'axis lie-A2, withinlimits defined by slot itl which is provided in base plate III. This rotation takes place about bolt H2 as apivot. bolt iubeing retracted to reduce the friction between washer its and the upper surface of base plate Hi during this rotation and being tightened after the desired adjustment has been attained.

In using the fixture to support crystal H3 during examination by "the conoscope described focused at the center of immersion tank H by lenses supported in lens tube It. will pass through lens 12 perpendicularly to the inner surface thereof and will not be bent or refracted, therefore, as they contact the immersion liquid (or fluid) contained in'the tank. (This follows from a fundamental law of optics, which states that if the incident ray is perpendicular to thesurface separating the two media, the ray is not refracted.) The light rays pass through the center point of the tank and strike the inner surface .of lens ll perpendicularly thereto so here again there is no bending or refraction of the rays as they enter the lens. (The rays are not bent or refracted as they pass from the liquid into the crystal and from the crystal back into the liqu d due to the fact that the liquid utilized is selected,

as pointed out above, to have a refractive index the same, or substantially the same, as that of the crystal.) It is apparent, therefore, that the focus of the instrument is independent of the the path of the light rays and the entire above.the assembly is placed in tank ii (Fig; l)

in a position similar to that of Fig. 4, quartz crystal H3 being immersed in -the fluid and in bly being supported through engagement of the two ends of base plate ill with respective lip portions provided near the top edge of tank Ii. If desired, positioning pins and registry holes may be provided for locating theassembly in the tank. 'Table I. and transparent end plate 39 may be removed from the tank during use of the fixture.

7 located, in the tank, the-.twb adjustments may The light source, polarizer, lens and analyzer of the conoscope aredia'grammatically illustrated in Fi 4. After the assembly has been properly then be effected until the desired positioning; or the concentric rings (optical), with respect to the cross-hairs of retlcule 11 (Fig. 1) indicating that the optical axis of'crys'tal Ill is parallel to the longer axis of base plate III has been attained. Platform-l l2 is-then locked in this adjusted position and the entire fixture assembly may be removed from the conoscope, inverted, and positioned in a saw for cutting desired sections from g the crystal. It is' assumed that suitable position time contained in the tank and will not be ing members will be provided on the work holder changed even though one immersion liquid may of the saw for proper orientation of base .plate III.

If a natural prism face of crystal I I3 is present, the crystal may, if desired, beattached to platform 2 by cementing the prism face thereto.-

In such event, crystal slabs of. a desired orientation may be sawed directly from the crystal after proper adjustments as provided for by the fix ture.

Referring now to Fig. 5, there is illustrated a scribed, for correction of a partially completed piezoelectric plate or blank in the event that the blank has been cut from the crystal with insufficient accuracy.

The correction fixture illustrated comprises base plate I upon which is removably mounted plate I42. A third plate I43 is adjustably supported by plate I42, plate I43 being tiltable withinlimits with respectto plate I42 by adjustment of bolts I44, I45 and I43.

These bolts are positioned in plate I42 with their tips projecting to engage the adjacent face of plate I43. The heads of the bolts are preferably provided with socket heads to facilitate adjustment. Plates I43 and I42 are secured together by bolts I41 and I43,

up of bolt in in a slot provided in the face" of plate I43 and by engagement of the. tip of bolt I45 in a conical depression provided in the face of plate I43. A centrally located aperture is provided in plate I43, the walls defining the aperture being sloped inwardly. An elongated U- shaped aperture is provided in plate I42.

In use, a partially completed piezoelectric plate or blank I'III is first cemented, or otherwise temporarily attached, toplate I43 centrally located with respect to the tapered end of the aperture provided in plate I43, the blank beingso positioned that its "X or electrical axis is parallel to the length of plate I43. Plate I42, which supp ts plate I43, is now assembled with base plate I, being rigidly positioned by registry of pin I", which is carried by base plate I with a properly located hole in plate I42 and by registry of a similar second pin and hole, not shown. The assembly is now placed in the conoscope tank, the under-side of base plate I being adapted to fit snugly down onto platform 24 (Fig. 1), after removal therefrom of table 33 and end plate 33 carried thereby. Platform 24 is now set for the desired angle of cut (represented schematically in Fig. 5 as i and if it be found that the interference rings are not properly centered on reticule 'I'I (Fig. 1), plate I43 may be tilted in the required direction or directions by adjustment of one or more of the three bolts I44, I43 and I43 (Fig. 5) until the interference rings are properly centered. The definition of the aperture through plate I43 by tapered or conoscope light source will not be blocked out by the plate when the ,fixture has been rotated correction fixture that may be used to advantage in connection with the conoscope, previously defrom the conoscope and placed in suitable grinding apparatus whereby the exposed face of blank .I'III is accurately ground parallel with the length of plate I42.

when the correction fixture is positioned on the platform of the conoscope, the entire assembly is ordinarily immersed in'the fluid with which the conoscope tank is filled. In order to facilitate adjustment of bolts I44, I45 and I43, while the fixture is immersed in the fluid, a tool of the nature illustrated in Fig. 6 may be used.' This tool comprises a driving shaft I62 with knurled finger grip anda driven shaft I 63 with a projection properly shaped to register with the socket heads of bolts I44, I43 and I43, the two shafts being mechanically coupled by miter gears I34 and IN.

While certain specific embodiments of the invention have been selected for illustration and detailed description, the invention is not limited in its application to such embodiments. The embodiments described should be taken as illustrative and not-restrictive.

What is claimed is:

1. An'immersion type conoscope for examining, crystals comprising an immersion tank, said tank having two ports at diametrically opposite points in the'slde wall thereof, an object supporting table within said tank, and two lens systems horizontally arranged with respect to said tank, a concavo-convex lens at one terminal of each of said lens systems, each of said terminal lenses being positioned in a respective one of the ports whereby the ports are effectively closed to the passage of fluids, said terminal lenses being so positioned with respect to each other and their respective inner surfaces being so shaped that they may be considered parts of the same imaginary spherical surface the center of which is within the light path through said lens systems and is so located with respect to said table as to lie within an object supported by said table whereby a ray of light projected from the center point of the imaginary spherical surface to the inner surface of either ofsaid terminal lenses 1 andunrefracted during travel from said center point to said inner surface will strike the respective inner surface at right angles regardless of its direction of projection.

2. An immersion type conoscope for examining whereby the ports are effectively closed to the sloping walls assures that the light from the passage of fluids, said terminal lenses bein mounted on a common'horizontal axis and bein so positioned with respect to each other and their respective inner surfaces being so shaped that a ray of light projected from a point in said tank which is located-on said horizontal axis mid-way between said lenses to the inner surface of either of said terminal lenses and unrefracted during travel from said point to said inner surface will strike said inner surface at right angles thereto regardless of its direction of projection.

3. An immersion type conoscope for examining crystals comprising a plurality of supporting legs, an immersiontank supported on said legs.

a rotatable object supportingtable within said other of said lens tubes, a hand-wheel for rotating said table located outside of said tank and a shaft operatively connecting said rotatable table and said hand-wheel, said shaft passing through the bottom of said tank whereby the interior of said tank is unobstructed thereby.

'4. An immersion type conoscope comprising an immersion tank, an object supporting platform rotatably supported within-said tank adjacent to the bottom wall thereof, said tank having two ports at diametrically opposite points in the side wall thereof, a source of light, a first lens tube, one end of said first tube being positioned in one of the ports, said first lens tube extending horizontally with respect to said tank, means in said first lens tube for polarizing light from said source, additional means in said first tube for convergin the light after polarization and causin it to enter said tank through said one of the ports in a cone of rays, a second lens tube, one

end of said second lens tube being p sitioned in the other of the ports, said second lens tube also extending horizontally with respect to said tank,

means in said second lens tube for analyzing light rays received from said tank, a hand-wheel for rotating said platform located outside of said tank, and a shaft operatively connecting said platform and said hand-wheel, said shaft passing through, the bottom wall of said tank whereby the interior of said tank is unobstructed thereby.

5. An immersion type conoscope for examining crystals comprising an immersion tank, said tank having two ports at diametrically opposite points in the side wall thereof, two lens systems horizontally arranged with respect to said tank, a 'ccncavo-convex lens at one terminal of each of said lens systems, each of said terminal lenses being positioned in a respective one of the ports whereby the ports are effectively closed to the passage of fluids, said'terminal lenses being so positioned with respect to each other and their respective inner surfaces being so shaped that .they may be considered parts of the same imaginary spherical surface, and means for adjustably supporting a crystal being examined in said tank, said supporting means comprising a base plate adapted to be supported by portions of the side wall of said tank, a mounting plate adapted to.

support acrystal adjustably supported by said base plate and means for producing selected 5 formupporting saidlight source in. spaced relationship to said tank, said tank having two ports at diametricahy opposite points in the side wall thereof, a first lens tube extending ,horizontally between one ofthe ports in the tank and said light source, a polarizer in said tube for polariz- -ing light from saidsource, said polarizer being rotatably mounted in said tube, a plurality of lenses in said tube for converging the light rays after polarization, one of said lenses being positioned in said one of the ports and completely closing it to passage of fluid, a second lens tube extending horizontally from the other port in said-tank, a plurality of lenses in said second tube for converging light rays passing therethrough, one of said lenses in said second tube being positioned in said other port and completely closing it to passage of fluid, an eye-piece mounted in the end of said second tube remote from said other port in said tank and alight analyzer positioned in said second tube between said eye-piece and said plurality of converging lenses, said analyzer being rotatably mounted in said second tube.

7. An immersion type conoscope for examin portingthe material being examined, said tank 1 having a light entry port and a light exit port in the wall thereof, a source of light, a first lens tube positioned between said light source and the light entry port, a second lens'tube communicating with the light exit port, a light polarizer in said first lens tube for polarizing light from said light source, means in said first tube for converging the polarized light to form a cone-shaped amounts of rotation of said mounting plate about two mutually perpendicular axes, the center of the imaginary sphere being within the path of light through said lens systems and being so located with respect to said mounting plate as to lie said inner surface will strike the respective inner surface perpendicularly regardless of its direction of projection.

6. In an immersion type conoscope for examin.

ing a crystalline material, an immersion tank for containing affiuid or a fluid and a solid, a specimen supporting table within said tank, a plurality of legs for supporting said tank, a light source, an extension arm on one oi said legs group of light rays and for projecting the rays through said immersion tank into said second lens tube, a light analyzer in said second tube, means in said second tube for projecting t e light rays through said analyzer to a focal point .01 fixed position, and means for maintaining the position of said focal point constant regardless of changes of the refractive index of a fluid or of a fiuid and a solidhaving corresponding refrac tive indices in said immersion tank.

8. An immersion type conoscope for examining crystalline material comprising an imon tank for containing a fluid or a fluid and a solid, a rotatable platform within said tank for supporting the material being examined, said tank having a light entry port and a light exit port in the wall thereof, a source of light, a first lens tube positioned between said light source and the light entry port, a second lens tube communicating, with the light exit port, a light polarizer in said first lens tube for polarizing light from said light source, means.

in said first tube for converging the polarized light to form a cone-shaped group of light rays and for protecting the rays through said im-* mersion tank into said second lens tube, alight analyzer in said second tube, means in said sec-.

ond tube for projecting the light rays through said analyser to a focal point or. fixed position,

and means for maintaining the position of said focal point constant regardless of changes of the refractive index or a fluid or or a fluid and asolid having corresponding indices in said immeraion tank, said last-mentioned means comprising a concave-convex lens positioned in the light entry port and an identical concavo-convex lens positioned in the light exit'port, said two lenses being mounted in face to-face relation-,

amining crystals, an immersion tank, a rotatable table within said tank, means outside said tank for rotating said table, means for passing rays of polarized light through said tank, and a p rp ndicularly crystal supporting fixture adapted to be removis ably mounted on said table and to be rotatable therewith when so mounted, said fixture including an apertured plateior supporting the crystal being examined in the path of said light rays when said fixture is mounted on said table, cooperating means for adiustably tilting said apertured plate about two mutually perpendicular axes in order to bring the crystal being examined into a particular adjusted position with respect to the path of said light rays, and means for locking said apertured plate in such adjusted position whereby said fixture may be subsequently removed from said table without disturbing the adjusted position or the crystal.

, WALTER L. BOND. 

